Care Of Cacti In Containers

Cacti are a group of succulent plants that do well in containers under the right conditions. They are native to the New World. These plants are diverse both in form and color, clumping or solitary. They can range in size from very small to more than 40 feet tall. Most cacti are best grown outdoors in filtered sun or on a bright patio. Some can tolerate full sun. Smaller species may be kept in a container. The larger varieties can start out containerized but will outgrow their pots and can be moved to the landscape, depending on the species, where they can enjoy more growing space.

SOIL: Most cacti should be grown in mineral-based soils consisting of a mixture of sands, silts, and gravel (good drainage) and which does not harden when dry. Cacti from tropical dry forests and high altitude regions benefit from a mix containing 25-50% decomposed organic matter. Epiphytic cacti such as Christmas cacti like a 1/3 – 1/3 – 1/3 mix of bark, pumice and decomposed organic matter. No peat should be used in any of these mixes. Organic matter consisting of well-decomposed plant material or worm castings is acceptable. If you wish to use peat-based soil mixes, you can, provided that you re-pot every 2-3 years. No commercial mixes come up to these standards as of this time, so you will need to formulate your own.

WATER: It is completely false that cacti need no water; after all, they are composed principally of water. What is true is that they require less water than violets, but more than a rock. Water cacti when they are actively growing or are wilting. Wilting appears as shrinkage of the plant or wrinkling of the surface. Most cacti grow actively in the spring and summer, but some grow in the other seasons as well so you will need to watch them carefully. Water only when the soil is nearly dry. You can test for dry sub-surface soil with your finger, a wooden pencil or popsicle stick (damp soil will cling to the wood), or (best) with a moisture meter. Water all of the soil thoroughly until the water runs out of the drain holes. Use only pots with drain holes, and if you use pots with saucers, be sure to empty the saucer after watering. The rule is ―no swamps.‖ The warmer the weather, the more frequently water is needed, unless the plant is dormant. In winter, little or no water is needed, even for cacti in active growth, because it is cool. Natural rain is very beneficial, and water may be applied from overhead (which helps clean the plant), at the soil line, or from below. Remember not to let the plant stand in a saucer of water.

LIGHT: Cacti, excepting epiphytes, are best grown outdoors. Interiors are usually too dark for good growth unless assisted by high-intensity lights. Cacti grown indoors very frequently develop pointy heads or other forms of stem stretching. Cacti should be grown outdoors in conditions ranging from full sun to 50% shade, depending on the species and on the size of the plant. If the cactus gets too much sun it will sunburn, which results in a yellowing of the skin, progressing to a browning (killing) of the skin on the sunniest side. If this occurs, provide shade immediately. Eastern exposures are gentlest, western sunlight is fiercest.

FERTILIZATION: Container grown plants need fertilizer because the soil will be exhausted of nutrients over time. The frequency of fertilization depends on how fast you want the plant to grow and the strength, or  concentration, of the fertilizer that you use. Remember that fast growth may produce weak cells, leading to over-tenderness. Fertilize at least once every four weeks during the plant’s growing season. Use the concentration recommended for ornamental plants on the fertilizer package. If you fertilize with each watering cut the strength of the solution accordingly. Use a low nitrogen fertilizer, such as 10-30-20. As a slow-acting organic fertilizer, fish emulsion is effective.

TRANSPLANTING/REPOTTING: Transplanting should be done when the plant has filled the pot, or, in the case of tall species, when the pot becomes top-heavy. If the soil in the new destination is the same or similar to that in which the plant is growing, simply shake the plant free of its container, keeping the soil ball intact if possible. Rough up the edges of the soil ball and then replant, keeping the soil level the same as the former location. If the soil/root ball collapses, wait a week to let the roots callus, then plant, using dry soil. If you are changing soil types from organic to mineral, first remove all old soil from the roots using an old toothbrush to get at the most stubborn bits. Cut off any broken roots and let dry until all wounds have callused over, then re-pot or plant using dry soil to fill in so that the soil will flow and fill in all air pockets. Wait a few days, then water in to settle the soil. It is best to transplant when the plant is actively growing, but if you must, you can do it anytime.

PESTS AND DISEASES: Cacti have few diseases and pests. Most problems are environmental. Pointy heads in globular cacti or stringy narrow stems in others–Etiolation caused by too little light–give more light. Yellowing or browning of the skin: especially on the sunny side—Sunburn—give more shade immediately. Wilting, wrinkling, shrinkage: dry soil, needs water. If the soil is wet, then roots have died due to swamping—remove from damp soil, re-root, and transplant. White cottony masses or white rice-like objects on plants: Cochineal scale or mealy bug—wash off with a hard jet of water, or apply alcohol or a pesticide for scale insects. Inspect plant often to check for recurrence. Very fine spider webbing in the spines: sometimes with red bead-size mites, and graying of the skin—Red spider mite. Wash off the water and use overhead watering to prevent reoccurrence. In severe cases use miticide treatment. Large larvae (grubs) tunneling inside stems, large black adults feeding on tips of plant: Longhorn beetle—remove adults at dawn and kill, or place them in a large prickly pear cactus clump some distance away.

Plant being eaten: Rabbit, rodent or javelina damage—Protect plant with a wire cage or move out of reach. Wet rot anywhere on the stem: Bacterial rot (Erwinia carnegieana)—Cut away all rotted tissue down to fresh, discolored tissue. Air dry. Do not fill in holes. Dry rot on tips or in the whole plant: Fungal dry rot (Helminthosporum cactivorum)—Cut away all dried and discolored tissue. Air dry.

Problem Guide For Southwest Gardens

A noticeable, fine web may be present on your Palo Verde trees (Parkinsonia spp.) and even from time to time on the Whitethorn Acacia (Vachellia constricta syn. Acacia constricta).  This “webbing” is produced by the Palo Verde webworms often called Palo Verde webbers. The webworm is a small caterpillar that feeds on the leaves and occasionally the bark of the small stems.  The Palo Verde tree and Whitethorn Acacia are resilient to webworm infestations so control methods are unnecessary. The caterpillars and adult moths are an important food source for many lizards and birds.
If you notice a tattered appearance on your landscape plants such as Evening Primroses (Oenothera spp.), Sacred Datura (Datura wrightii) and Gaura (Gaura lindheimeri) it may be the flea beetle in action. A different species of flea beetle may also harm your vegetables including tomatoes and eggplants. The flea beetle larvae and adults can be destructive and they can be difficult to control. To find out more information on flea beetles go to the following link:
Agave snout weevils become active during the warm months and infestation may not be apparent until it is too late. For detailed information on the life cycle, symptoms,
While sitting underneath your desert trees, you may notice a light “rain” falling. This is the smoke tree sharpshooter insect expelling sap as it draws from a variety of plants including Palo Verdes (Parkinsonia spp.), Beebrush (Aloysia gratissima), Bird of Paradise species (Caesalpinia spp.) and Hackberries (Celtis spp.). These sharpshooter insects have gone virtually unnoticed until they threatened oleanders, shrubs widely used in low-desert landscapes for screening hedges. They gained notoriety because they are able to transmit a deadly bacterial disease called oleander leaf scorch. Our native plants do not appear to be adversely affected by the smoke tree sharpshooter so no control is necessary.  To find out more about oleander leaf scorch check out the University of Arizona Extension Plant Pathology at
As the weather warms, whiteflies may be present on your landscape, vegetable and herb plants. These tiny, white insects have sucking mouthparts that cause leaves to yellow, wilt and drop prematurely. The immature nymph stage does more harm to the plant than the adult. Whiteflies can be difficult to control. Allow natural predators such as spiders, ladybugs, lacewings and even hummingbirds to control the population. Yellow sticky traps can also be used to control the adult population.
Noticeable leaf damage may be seen on the Texas Mountain-laurel (Calia secundiflora syn. Sophora secundiflora) during the warm months. The damage is caused by the sophora pyralid caterpillars feeding on the tender new growth. These ravenous caterpillars are approximately an inch long with orange bodies and interesting black spots with white hairs.
Psyllids can still be active during the month of May, but activity will decrease as the temperatures climb.  Psyllids are sap feeders and many are plant specific or feed on a closely related group of plants. High populations of psyllids can cause distortion and die back of new growth, and in some cases defoliation. To keep populations under control do not overwater or over fertilize your plants as this causes excessive growth. Yellow sticky traps can also be used to control the adult population.
Cochineal scale, the cottony, white substance on your Prickly-pears (Opuntia spp.) and Chollas (Cylindropunita spp.) may be active now. Remove by using a fast stream of water or spray insecticidal soap.
Fine webbing between leaves or stippling on leaves may indicate the presence of spider mites. These plant mites cause damage by sucking contents from the leaves and are difficult to detect due to their small size. Plants that are water stressed may become susceptible to infestation. Dusty conditions can also lead to spider mite outbreaks. Make sure your plants are well-watered and wash off accumulated dust on plants to manage spider mite problems. You can also remove by using a fast spray of water or by spraying insecticidal soap to control populations. There are many biological controls that feed on spider mites including lacewings, predatory mites, lady bugs and big-eyed bugs. Using insecticides is not recommended as insecticides do not help manage the population, but can actually cause the population to intensify because insecticides used will often kill their natural enemies. Some insecticides can even accelerate mite reproduction.
If you notice a rank odor and black ooze dripping down the saguaro stem(s), the plant may have developed an infection as a result of an injury or frost damage. The infection is caused by the Erwinia bacteria, a common bacterium found in the environment.
For more information on diseases or problems of landscape plants go to the University of Arizona Cooperative Extension publication/sites/dbg.dd/files/pldiseases_urban-1124.pdf or the University of California UC IPM Online at

What To Plant In May

Planting can still be done during the month of May. However, it is crucial that newly planted plants are monitored carefully. Follow the watering schedule for newly planted plants in the watering section.
When planting native and desert-adapted plants, it is usually unnecessary to back-fill with soil amendments and vitamins or to add rooting hormones. However, a slow-release fertilizer high in nitrogen and phosphorous can be added to the backfill, if needed. 
Many cacti can be started from seed at this time.  Seed can be soaked overnight in water to help start the germination process. Place seed in a well-draining soil mix (½ quality potting soil and ½ perlite or pumice) and lightly cover with potting mix or gently press the seed into the soil. Keep soil moist until germination occurs.
• Mexican Hat (Ratibida columnifera)
• Red Sage (Salvia coccinea)
• Desert Senna (Senna covesii)
• Sacred Datura (Datura wrightii)
• Mealy-cup Sage (Salvia farinacea)
• Jerusalem artichoke
• sweet potato
• watermelon
• tomatillo
• jicama
• eggplant and pepper (by mid-month)
• Black-eyed peas (early part of May)
• cantaloupe
• okra
• tepary beans
• muskmelon
• tomatillo
• yardlong bean
• pumpkin
• summer and winter squash
• watermelon
Try the variety of melons from Native Seeds/SEARCH.
• basil
• Mexican-oregano (Lippia graveolens)
• Mexican-tarragon (Tagetes lucida)
• Cuban-oregano
• amaranth
• Saguaro (Carnegiea gigantea)
• Prickly-pears (Opuntia spp.)
• Chollas (Cylindropuntia spp.)
• Barrel cacti (Ferocactus spp.)
• Hedgehogs (Echinocereus spp.)
• Pincushions (Mammillaria spp.)
• Easter Lilies (Echinopsis spp.),
• Paper-spine Cholla (Tephrocactus articulatus var. papyracanthus)
• Agaves (Agave spp.)
• Aloes (Aloe spp.)
• Candelilla (Euphorbia antisyphilitica)
• Desert Spoon (Dasylirion wheeleri)
• Giant Hesperaloe (Hesperaloe funifera)
• Slipper Plant (Pedilanthus macrocarpus)
• Elephant Food (Portulacaria afra)
• Burseras, Elephant Trees (Bursera spp.)
• Madagascar-palm (Pachypodium lamerei)
• Madagascar-ocotillo (Alluaudia procera)
• Dyckia spp.
• Carrion Flowers (Stapelia spp.)
• Texas-tuberose (Manfreda maculosa)
• Limberbushes (Jatropha spp.)
• Red-yucca (Hesperaloe parviflora)
Most Yuccas (Yucca spp.) can be planted with the exception of Joshua Trees (Yucca brevifolia).
When transplanting cacti and succulents, mark either the south or west side and plant facing the orientation you marked to avoid the burning of tender tissues. Most nurseries will mark the side of the container to help you determine proper planting orientation. However, if the original orientation is not known, newly planted cacti and succulents need to be covered with shade cloth if the plant surface appears to yellow or pale suddenly. Use a shade cloth rated between 30-60% as anything higher will block most of the sunlight and will not be suitable for your cacti and succulents. You may need to keep the shade cloth on the plant for the duration of the summer.
• Ironwood (Olneya tesota)
• Blue Palo Verde (Parkinsonia florida)
• Little-leaf Palo Verde (Parkinsonia microphylla)
• Mesquites (Prosopis spp.)
• Golden Leadball Tree (Leucaena retusa)
• Desert-willow (Chilopsis linearis)
• Palo Blanco (Mariosousa willardiana syn. Acacia willardiana)
• Catclaw Acacia (Senegalia greggii syn. Acacia greggii)
• Canyon Hackberry (Celtis laevigata var. reticulata syn. Celtis reticulata)
• Texas-ebony (Ebenopsis ebano)
• Twisted Acacia (Vachellia bravoensis syn. Acacia schaffneri)
• Feather Tree (Lysiloma watsonii)
• Anacacho Orchid-tree (Bauhinia lunarioides)
• Vitex (Vitex agnus-castus)
• Baby Bonnets (Coursetia glandulosa)
• Yellow Bells (Tecoma spp.)
• Texas-sages (Leucophyllum spp.)
• Creosote (Larrea tridentata)
• Superstition Mallow (Abutilon palmeri)
• San Marcos Hibiscus (Gossypium harknessii)
• Desert Cotton (Gossypium thurberi)
• Guayacán (Guaiacum coulteri)
• Sennas (Senna spp.)
• Velvet-pod Mimosa (Mimosa dysocarpa)
• Ocotillo (Fouquieria splendens)
• Fire Bush (Hamelia patens)
• Ruellia (Ruellia peninsularis)
• Lantana (Lantana camara)
• Mexican Bush Sage (Salvia leucantha)
• Silver Nightshade (Solanum hindsianum)
• Little-leaf Cordia (Cordia parvifolia)
• Showy Mendora (Menodora longiflora)
• Sky Flower (Duranta erecta)
• Bird of Paradise species (Caesalpinia spp.)
• Sacred Datura (Datura wrightii)
• Desert Four O’Clock (Mirabilis multiflora)
• Arizona Foldwing (Dicliptera resupinata)
• Buffalo Gourd (Cucurbita foetidissima)
• Mealy-cup Sage (Salvia farinacea)
• Yerba Mansa (Anemopsis californica)
• Rose-mallow (Hibiscus coulteri)
• Wine Cups (Callirhoe involucrata)
• Hummingbird Trumpet (Epilobium canum ssp. latifolium)
• Chocolate Flower (Berlandiera lyrata)
• Desert Senna (Senna covesii)
• Trailing Lantana (Lantana montevidensis)
• White Plumbago (Plumbago scandens)
• Mist Flower (Conoclinium dissectum)
• Rain-lilies (Zephyranthes spp.)
• Yuca (Merremia aurea)
• Queen’s Wreath (Antigonon leptopus)
• Yellow Orchid-vine (Callaeum macropterum)
• Passionflowers (Passiflora spp.)
• Arizona Canyon Grape (Vitis arizonica)
• Old Man’s Beard (Clematis drummondii)